1. So if we were designing a heparinase reactor how would we get the beads
containing the immobilized enzyme in a well-mixed state?
The paper by Langer’s group, ie. Ameer et al (I) looked at fluidization of
whole blood in a Taylor-Couette Flow Device
The Taylor vortices would facilitate the fluidization of the agarose beads and
lead to a well-mixed reactor
Taylor vortices are flow instabilities that occur within an annular gap of
concentric cylinders when the inner cylinder is rotated above a critical
rotation rate

2. Factors affecting the fluidization
of the beads included:
Gap space, 3.2 mm and 6.4 mm
Rotation rate of inner cylinder
Flow rate of blood thru the device

3. Results and Discussion
Immobilization bound 95% of the soluble enzyme and retained 30-40%
of the enzyme activity
2. Over a 4 day period of operation no leaching of the enzyme from the agarose
was detected
3. Heparin degradation products were found to be nontoxic at [ ]’s up to
100x’s the expected levels during clinical exposure
4. Phase I clinical trials in healthy volunteers showed no acute reactions when
exposed to soluble heparinase which was obtained from Flavobacterium
heparinum

4. Narrow gap
90% removal of heparin in 3 minutes

8. Attempted to reduce blood damage in this initial design by:
Increasing the gap width while maintaining annular volume constant
Reducing the rotation rate
Note that conversion is now about
80% at 3 minutes

9. Note that Hb release is significantly reduced between
design I and design II

10. Blood cell damage reduced from design I to design II

11. Constant flow showed about a 23% per pass removal
Clinical application needs about 45%

12. Although Taylor vortices are usually gentle to RBC’s this study showed
that when used in combination with the agarose beads hemolysis of
the RBC’s is a big problem.
So, how would you solve this problem?
The next paper by the same group and labelled II illustrates how
they attacked this problem
Design criteria:
efficacy, need a 40-50% per pass heparin conversion
Safety, no significant effect on whole blood cells, no hemolysis,
no reduction in platelets or white blood cells, and no activation of
these cells either
3. stability, stable operation at flowrates up to 300 ml/min
4. simplicity, simple operation and low cost
To minimize blood damage, a device that SIMULTANEOUSLY effected
plasma separation and the enzyme reaction with the capacity to treat
whole blood at high flowrates was designed.

14. Previous
paper
Poor mass transfer and
loading issues
Blood cells and the
platelets would not come
into contact with the agarose
beads and hence minimize
hemolysis

17. Conversion about 34% and below their target of 40-50%, but could be
increased by adding more beads

18. Eliminating contact between the cells and the agarose beads as in this
design was an effective way to significantly reduce hemolysis.